Various industrial processes, such as semi-conductor fabrication, generate wastewater having high concentrations of suspended and dissolved solids. Such wastewater can be highly toxic, and accordingly must be purified prior to being sent to municipal wastewater treatment plants.
An industrial process known as Chemical Mechanical Planerization or polishing, (CMP) is one for which purification of the wastewater stream is of particular interest. CMP, which can be used in the fabrication of integrated circuits having copper interconnects, removes excess copper by a hybrid process where copper is polished off the semi-conductor wafer by a combination of chemical etching and physical polishing by fine aluminum oxide slurry. The particle size distribution of the slurry ranges generally from 0.02 micron (200 Angstroms) to 0.10 micron (1000 Angstroms). The rinsewater wastes contain variable amounts of dissolved copper salts in addition to the suspended solids of the slurry.
Purification of the rinsewater from CMP processes presents a significant challenge for waste disposal efforts. It is desirable to remove the suspended and dissolved solids from the CMP rinsewater stream. However, the solids present in the rinsewater can plug the flow path of conventional purification systems, such as filter membranes and ion-exchange resin columns, thus making such processes for removing wastes from the CMP rinsewater highly inefficient. Further, conventional ion-exchange resins can be irreversibly damaged by oxidizers that are commonly present in CMP rinsewater. While activated carbon is often used to eliminate oxidizers from waste streams, the pores of activated carbon particles are susceptible to plugging in CMP rinsewater due to the particle size distribution of the CMP slurry waste. Additionally, the use of conventional ion-exchange resin technology requires intermittent interruption of the purification process for regeneration of the resin, thereby decreasing the efficiency of the process.
Accordingly, there remains a need to provide a new and improved method of purifying wastewater streams containing both suspended and dissolved solids, and CMP slurry in particular. There is a further need for methodologies for purifying and recycling the wastewater from industrial chemical processes. Additionally, there is a need for a new and useful apparatus for use with the methods of the present invention for the treatment and processing of water containing suspended and dissolved solids, such as the wastewater from copper CMP manufacturing processes. The present invention is directed to meeting these needs.